1. Field of the Invention
This invention relates to spherical bearings and a method for making such bearings with seals for preventing the entrance of grit or other deleterious materials between slidably engaged bearing surfaces.
2. Description of the Prior Art
Spherical bearings of the type to which the present invention relates include an inner bearing element, usually a truncated ball, and an annular race that receives the inner bearing element so that slidably engaged surfaces permit relative movement between the bearing element and the race. While bearings of this type are commonly referred to as spherical bearings, they are also referred to as self-aligning rod ends. One type of such bearing has spherical metallic surfaces of the bearing race and the inner bearing element engaged directly with each other to provide the rotatable support that permits the relative movement between the bearing components. Often a grease or oil fitting is provided for introducing lubricant between the spherical metallic surfaces of this type of bearing in order to reduce the friction which resists relative movement between the bearing components. Low friction characteristics without lubricants is also possible by lining the inner spherical surface of the race with a low friction material. Such linings can consist of mixtures of organic resins such as, for example, a mixture of particulate polytetrafluoroethylene and a phenolic or other thermosetting or thermoplastic resins or such linings can consist of other materials or a combination of materials to provide the desired low friction characteristics along with the required compressive strength and other necessary physical properties. The preferred and most commonly used low friction linings for such bearings are formed of cloth which includes polytetrafluoroethylene fibers or threads and preferably also fibers or threads of more bondable material, impregnated with and bonded to the interior surface of a race by a hardened organic resin such as a phenolic resin. Such bearings and bearing liners are the subject matter of U.S. Pat. Nos. 2,885,248, Re. 24,765, and 3,037,893.
Regardless of whether spherical bearings are of the lined or unlined type, it is important to prevent the entrance of grit, organic solvents or other deleterious materials between the spherical bearing surfaces. To prevent this entrance, prior art bearings have incorporated seals secured with respect to the outer race and slidably engaged with the outer spherical surface of the bearing element. Heretofore, these seals have been premolded and then secured with respect to the race so as to slidably seal with the bearing element. Examples of such seals are shown by U.S. Pat. Nos.3,243,212 and 3,873,166.